The present invention relates generally to suspension systems for vehicles and more particularly to suspension systems for agricultural tractors and other off-road vehicles.
In the farm machinery sector, agricultural tractors are well-known typically comprising front and rear laterally extending axles having wheels rotatably affixed at the ends with a longitudinally elongated box body, or chassis, connecting the axles. Rear axles are commonly rigidly connected to the chassis, there is no suspension between the rear axle and the tractor frame. Tire deflection alone provides a cushioning between a rough surface and the tractor frame. In many tractors, the front wheels are driven in addition to the rear driven wheels, the tractor having four wheel drive. Economics and simplicity typically dictate that rigid front axle assemblies be used in lieu of an independently articulated front suspension. Front axles are typically hingeably attached to the front of the tractor chassis to rotate, transversely with respect to the longitudinal axis of the chassis, around a respective hinge axis located proximate to the longitudinal middle of the axle. With this axle structure, when one front wheel is raised to overcome an obstacles the other front wheel has to come down the same distance.
The productivity of an agricultural tractor can be increased by enabling faster travel speeds in the field and on the road. Limiting factors to the travel speed of an agricultural tractor when traveling over rough surfaces are operator comfort and wheel traction. Faster travel speeds highlight shortcomings in the conventional hingeably-attached rigid front axle, especially when both wheels simultaneously encounter a similar obstacle, such as a ditch. When both wheels must move in the same direction to traverse an obstacle, the entire front end of the vehicle is forced to move in the same vertical direction,
Tractor front axle suspensions solve these problems by enabling the entire axle to move in relation to the tractor frame. By damping such motion traction and operator comfort may be increased both of which may contribute to increased productivity. Additionally, front axle suspensions for tractors provide better high-speed handling characteristics during high-speed operation on roads. The addition of more sophisticated actuators and control systems to these suspension systems further extend the capabilities of the tractor and provide additional improvements in vehicle ride and handling.
It would be a great advantage to provide an active suspension system for a rigid beam tractor axle that increases traction, improves the ride and handling characteristics of the tractor, and provides sufficient wheel turning capability to retain accepted vehicle maneuverability, all while retaining a simple, cost-effective rigid front axle member to overcome the above problems and disadvantages.